Mark a layout test virtual/threaded/fast/compositorworker/visual-update.html as flaky

Bug: 727991
Change-Id: Ife0e27562727cf08ff40615baf3f024ed621534d
Reviewed-on: https://chromium-review.googlesource.com/518745
Reviewed-by: Yutaka Hirano <[email protected]>
Commit-Queue: Takeshi Yoshino <[email protected]>
Cr-Commit-Position: refs/heads/master@{#475836}
diff --git a/third_party/WebKit/LayoutTests/TestExpectations b/third_party/WebKit/LayoutTests/TestExpectations
index 2041a90..2d0a933e 100644
--- a/third_party/WebKit/LayoutTests/TestExpectations
+++ b/third_party/WebKit/LayoutTests/TestExpectations
@@ -3036,3 +3036,6 @@
 # Sheriff failures 2017-05-30
 # Failing on try (with patch) and Linux FYI too frequently.
 crbug.com/727505 [ Linux ] virtual/threaded/fast/compositorworker/basic-plumbing-main-to-worker.html [ Pass Crash ]
+
+# Sheriff failures 2017-05-31
+crbug.com/727991 [ Linux Mac ] virtual/threaded/fast/compositorworker/visual-update.html [ Pass Failure ]